In a relational database context, rollup operations can be performed against a given set of rows. The rollup operations can be specified in a database statement. For example, specifying a ROLLUP keyword in a GROUP BY clause of an SQL SELECT statement causes performing two or more group-by operations as a part of executing the SQL SELECT statement. The rollup operations generate multiple levels of subtotals based on a list of rollup columns specified in the database statement. The multiple levels of subtotals generated by the rollup operations can range from the most detailed level to a grand total from all rows used to evaluate these subtotals.
Rollup operations are frequently used for analyzing data sets. For example, rollup operations may be used to extract information on sales data stored in a database system. This information can be utilized by a company to track sales, evaluate policy, develop marketing strategy, project future growth, and perform various other tasks.
Given the importance of rollup operations for data analysis, providing a quick result for database queries specifying rollup operations is often an important database performance metric.
Based on the foregoing, there is a need for developing techniques that can perform rollup operations in a highly efficient and scalable fashion.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.